Transportation accounts for about 57 percent of the
carbon dioxide (the primary pollutant responsible for
global warming) produced in California. That figure far
outpaces the national average of 32 percent for two
reasons, one positive and one negative. The good news is
that California's electric power plants are cleaner than
those of other states, producing far less carbon
dioxide. That means carbon dioxide emissions from the
combustion of gasoline are a larger share of a smaller
pie.
On the other hand, California's growing population is
driving longer distances and spending
more time in cars. The number of licensed drivers
statewide increased 31 percent from 1980 to 1997, and
population growth continues -- over the next 20 years,
the Bay Area population is expected to increase by 14
percent. On top of this, the number of cars per
household and the amount of driving per person have
increased. What's more, traffic congestion wastes
hundreds of millions of gallons of fuel -- in 1997
alone, some 280 million gallons, or approximately 91
gallons of excess fuel per driver.
Yet another factor is at play: decreasing fuel
efficiency. This drop is a disturbing reversal of the
longstanding trend toward greater efficiency, which
resulted from federal legislation in the 1970s requiring
auto companies to increase the average fuel efficiency
of their vehicles. Although overall average fuel economy
increased from 17.6 miles per gallon in the mid-1970s to
20.6 miles per gallon today, the popularity of
sport-utility vehicles, which are held to less stringent
fuel-efficiency standards, has driven down the average.
As a result, average new-vehicle fuel economy is at the
lowest point in 20 years.
All this travel and gasoline consumption comes at a
high price, and not just at the pumps. While California
has made great strides in cleaning up smog and soot,
air pollution still threatens millions of state
residents, about 90 percent of whom live in places,
including the Bay Area, where the air is periodically
unhealthy to breathe. Gasoline engines are primary
sources of toxic air contaminants such as benzene and
butadiene, which are known to cause cancer in humans,
and respiratory irritants such as formaldehyde and
acrolein. And carbon dioxide emissions from Bay Area
vehicles also contribute to global climate change, which
will have profound effects on our local climate
and environmental health as well. Among the possible
regional consequences: loss of coastal and bay wetlands,
flooding in coastal areas, and salt-water intrusion that
could threaten drinking water and agricultural land in
the delta, the area where the Sacramento and San Joaquin
rivers come together and flow into San Francisco Bay.
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